Method of controlling the distribution of electric discharges



1 0 6 84 c oss REFERENCE EXAMINER Feb. 1 1927. 1,616,044

E. L. HARRINGTON METHOD OF CONTROLLING THE DISTRIBUTION OF ELECTRIC DISCHARGES I Filed March 22'. 1921 mvsmoa' 12745 L 7 HERE/N6 701v M ta! ple,.as tungsten. The en Patented Feb. 1, 1927.

UNITED STATES PATENT OFFICE.

EBTLE LESLIE HAR BINGTON, OF SASKATOON, SASKATCHEWAN, CANADA, ASSIGNOB TO WESTINGH OUSE LAMP COMPANY, A QOBPOBATION OI PENNSYLVANIA.

' METHOD 0! CONTROLLING THE DISTRIBUTION OF ELECTRIC Application filed. March 22, 1921. Serial No. 454,388.

The present invention relates to electrical devices employing an electron-emitting body, and more particularl to electric are devices having an incan escent cathode.

An object of my invention is the provision of a method for increasing the life of such devices.

My improvement will be understood and appreciated by reference to the following description of a specific example illustrative of m invention. In connection with this description, I have shown diagrammatically in the accompanying drawing, a device containing an incandescent cathode a ortion of which contains a material having igh electron-emitting properties.

The device comprises an envelope 1, preferably of lass, which contains a filling 0 any suitaliie gas, such as argon. A filamentary cathode 9, adapted to be heated to incandescence electrically, consists of a highly refractory material such, for examds of the cathode 2 are welded to leadin -in conductors 3, 4 which are preferably 0 '-a refractory mate rial. The anode 5 consists ofconductive'material, such as carbon, tungsten, or other refractory material. The cathode currentsupplywires 3, 4 and the anodeconductor' 6 are sealed intostems 7 and 8, respectively in the usual manner.

In the operation of devices of this character prior to m invention, the arc between electrodes tende to concentrate on a limited ortionv of ,the cathode, thereby causing a ocalized electrical disintegration which re-.

sulted in a division of the cathode into two parts, by which the usefulness of the device was destroyed.

In electricam devices, the arc tends to take the path of. least resistance. If an electrode of a given material has a non-uniform temperature or is not atthe same pothe concentration of the are at that tential at'all points, a point will exist on this electrode from which electrons will most.

copiously be given ofi, thereby providing a path of least resist-ante and resulting in point. This concentration of the are still further augments the. non-uniformit of tern rature and results in a localiz' electrica disintegration of the electrode which it is de' sired to avoid. These conditions existed-in devices similar to the one described above prior to my invention, inasmuch as the tempgrature of the cathode was non-umform 1 cause of the conduction of heat from it through its leading-in conductors causing the ends of the cathode to be at a much lower temperature than its central portion, and be ing heated electrically,the cathode also had a otential gradient so that the potential di erence was not the same uantity between the anode and all points 0 the cathode.

The electronic emissivity of a substance, i. e., the number of electrons emitted per unit area in unit timei depends on the nature of the substance an its tem rature. As to the nature of electron emitting bodies,

- it is known that certain substances, when hot, emit electrons in greater numbers than For instance, sodium, potassium and manyoxides, emit electrons at anelevated temperature more copiously than other materials, such, for exam le, as tun en at the same temperature. t is also own that electrons are emitted from a given substance more copiously as the temperature is increased. I

In devices employing eIectron-emittizg bodies in which the electrons are transmitt either through a vacuous space or. through a gas, the voltage drop .or loss in the are for a given value of current is less when electrons are copiously 'ven off from the electron-emitting body t an when the electronic emisivity is lower. It is, therefore, advantageous to employ bodies which emit electronsin great numbers, other factors being satisfactory.

My vention resides in providing an electrode of such anature that an arc will tend to be uniformly distributed over it, resulting in a gradual and uniform disintegration of the cathode, thereby giving it a longerf. other substances at the same temperature.

the relatively cool parts of the cathode,-

thus decreasing theelectrode reluctance at an electrode with medial and end these points, thereb equalizi the are drop between the anode nd VaIiOI I S points of the cathode and tending to spread the arc uniformly over the cathode. A variety of substances ma be used for this purpose but it hasthbeen found that ceiitain oxides such asose o sgggtmrn ca mum and Enum are well a apted to purpose.

I have used a mixture consisting of one part by weight of thorium oxide to 9 parts of metallic tlmgfin powder applied with asm e in er, suc assodium silicate, and permanently fixed on the cat e an eads y being fused thereon bymeans of an electricarc. Thetungsten powderisnsedas a mixture withl the thorium oxlilde tod assist mpermanent inco rati t e oxi einto the cathode. y ng In a cathode treated as above described the electronic emissivity of the ends of the cathode leading-in conductors and the cooler parts of the filament is so materially in-. creased, due to the reduction of the thorium oxide to thorium metal, that it becomes comparable with that of the hotter medial or inner section of the filament, thereby resulting in a uniform distribution of the arc, by

which a more durable cathode and, therefore,

a device of longer life is secured. whatisclaimediszn Y '1. In an electron-discharge device, having portions,

- means for prolonging the life of said device which consists in an additional material' of higher electron-emissivity than said medial portion ap lied adjacent the end portions only of t e electrode to prevent localiz ed dlsintegration of said electrode.

, 2. In an electron-discharge device, an elec- .trode comprising a coil of refi'actorymet'al the end turns only of which have applie thereto an additional material of higher electron -einissivity than said refractory metal.

3.. In an electron-discharge device, an elec-' trode comprising as a discharge part, .a

y of're ractor material containadjacent the ends 0 he discharge part a substance of higher electron-emissivity than said material.

4. In an electron-dischar device, an electrode heated .to' a non-uni orm temperature operation, but of com to materialof di erent electron emissivities, so as to have a substantially uniform electron flow 5. In an electron-discharge device, an electron-emitting electrode com rising a com-' posite body of materials of diflerent electron emimivities, heatedto a non-uniformtemperature, during peration, said lower telne- Pat i e electron.

- tron-emitting cathode, part of which is relaflow is secured therefrom.

only of said cath emission so that a substantially uniform electron flow is obtained from the electrode.

6. In an electron discharge device an electively hot and another part relatively c001 during operation, the cooled part only being coated with a material of higher electron-emissivity than the remainder thereof, whereby a substantially uniform electron 7. An electron-emi cathode consistin of a coil of aving medial and en turns, the end turns only of which are coated with a substance of higher electronemissivi than tungsten.

8. An electron-discharge device comprisinga sealed envelope containing an mert gas, a comparatively cool anode and a cooperating coiled incandescent cathode therein having medialand end turns, the axis of the cathode being ap roximately parallel to the adjacent face 0 the anode and the end turns only of the cathode being treated to increase their electron-emissivity, whereby concentration of. the discharge on the central turns of said cathode is prevented.

9. An electron-discharge device comprising a sealed envelope containing an inert gas, an anode operable below the, temperature at which appreciable electron-emission occurs and an incandescible mthode consisting largely of refractory metal containingan additional. material ofhigher electronemissivity only on the end turns thereof.

10. An electron-discharge device comprising a sealed envelope containing an mert gas, a relatively cool anode and an incandescent cathode consisting largely of tungsten coated only on the end portions thereof with a material of hi her electron-emissivity than tungsten, where y concentration of the discharge on the central portion of said cathode is avoided; 11. The method of making an electrode which will cause an electron discharge to be more uniformly distributed over it, which consists in coatin only the end portions of anode and a cooperating coiled incandescent cathode. in an electron-discharge device, which consists in a plying to the end-tn odia, a subs'tancezof hig er electron-emisivity than the base material of- Blidcathode. 4

In testimony whereof, I have hereunto name this seventeenth. ay

subscribed my of February 1921. 

